Dairy wastewater treatment requires a process designed around the wastewater’s organic load, fat content, suspended solids, and fluctuating pH. Without appropriate treatment, wastewater from milk processing, cheese production, and equipment cleaning can place a significant burden on treatment systems and receiving water bodies.
A study published in Food Technology and Biotechnology identifies mechanical, physicochemical, and biological processes as important approaches to dairy wastewater management. However, treatment performance depends on the wastewater composition, flow variations, and the combination of technologies used.
For dairy manufacturers, the priority is to identify the wastewater characteristics that affect treatment performance and arrange the treatment stages accordingly. This helps maintain stable operations, manage pollutant loads, and achieve the required effluent quality before discharge.
Characteristics of Dairy Wastewater
Dairy wastewater is generated during milk processing, product separation, equipment washing, and cleaning-in-place (CIP) activities. Its composition varies depending on the products manufactured, production schedules, and cleaning procedures.
Understanding these characteristics is essential for selecting an appropriate treatment process.
1. High Organic Load
Milk and dairy products contain lactose, proteins, and fats. When these substances enter wastewater, they increase its biological oxygen demand (BOD) and chemical oxygen demand (COD).
BOD indicates the oxygen required by microorganisms to break down biodegradable organic matter, while COD measures the oxygen equivalent required to chemically oxidize substances in the wastewater.
High BOD and COD can increase the treatment system’s workload and deplete dissolved oxygen in receiving water bodies if the effluent is inadequately treated.
Treatment implication: Organic loads must be reduced through appropriate pretreatment and biological processes. For concentrated wastewater, anaerobic treatment may be considered before aerobic treatment, depending on the wastewater composition and required effluent quality.
Read Also: Cleaning and Sanitizing in Food Manufacturing
2. Fats, Oils, Grease, and Suspended Solids
Milk residues, cream, butter, and cheese processing can introduce fats, oils, grease (FOG), and suspended solids into wastewater. These materials can accumulate in tanks and pipes, interfere with treatment processes, and increase sludge production.
Their concentration depends on the production line and the amount of product lost during processing and cleaning.
Treatment implication: Screening, solids separation, grease removal, or physicochemical processes such as coagulation and flotation may be required to reduce the load entering downstream treatment units.
3. Fluctuating pH and Cleaning Chemicals
Dairy facilities use acidic and alkaline cleaning agents to maintain equipment hygiene. When wastewater from different cleaning cycles enters the treatment system, its pH can fluctuate significantly.
Residual sanitizers and cleaning chemicals may also affect the microorganisms responsible for biological treatment.
Treatment implication: Flow equalization and pH adjustment help stabilize wastewater conditions. Cleaning discharges should also be managed to prevent sudden chemical or hydraulic shocks to the treatment system.
4. Variable Flow and Nutrient Concentrations
Wastewater generation often follows production and cleaning schedules. As a result, flow rates and pollutant concentrations may change throughout the day.
Dairy wastewater can also contain nitrogen and phosphorus. Although these nutrients can support microbial growth, excessive concentrations may require additional removal to meet discharge requirements.
Treatment implication: Equalization, appropriate biological process selection, and effluent monitoring help accommodate operational variations and maintain treatment performance.
These characteristics are discussed in research on dairy wastewater composition and treatment technologies. Their combined effects make it important to assess the actual wastewater rather than select a treatment system based on industry averages alone.
Read Also: Biological Nutrient Removal in Wastewater Treatment
Dairy Wastewater Treatment Stages
An effective dairy wastewater treatment system combines processes according to the wastewater characteristics, treatment objectives, available space, and applicable discharge requirements. The following stages provide a general framework for industrial dairy facilities.
1. Preliminary Treatment and Screening
The first stage removes coarse solids and debris before wastewater enters downstream treatment units.
Screens and collection systems can capture larger particles, while suitable separation equipment may be installed to manage solids and floating fats.
This stage helps reduce physical obstructions and limits the accumulation of unwanted materials in pumps, pipes, and treatment tanks.
2. Flow Equalization and pH Adjustment
After preliminary treatment, wastewater is collected in an equalization tank to balance variations in flow and pollutant concentration.
Mixing helps maintain a more consistent wastewater composition, while pH adjustment can bring the wastewater into a suitable range for subsequent treatment.
This stage is particularly important when production and CIP activities generate wastewater with different flow rates, temperatures, or chemical characteristics.
Proper equalization reduces the risk of sudden loading changes that can disrupt biological treatment.
3. Physicochemical Treatment
Physicochemical treatment is used when suspended solids, emulsified fats, or other separable contaminants need to be reduced before biological treatment.
Depending on the wastewater characteristics, the process may involve coagulation and flocculation, sedimentation, or dissolved air flotation (DAF).
Coagulation destabilizes fine particles, while flocculation encourages them to form larger aggregates that can be separated. DAF uses air bubbles to help float suitable suspended particles and fats to the surface for removal.
The appropriate configuration depends on the type and concentration of contaminants. This stage can reduce the pollutant load entering the biological system, although it may require chemical dosing and produce additional sludge.
4. Biological Treatment
Biological treatment uses microorganisms to break down biodegradable organic matter and reduce BOD and COD.
Two common approaches are aerobic and anaerobic treatment.
- Aerobic treatment: Uses microorganisms in the presence of oxygen. Activated sludge systems and sequencing batch reactors (SBRs) are examples that can be applied to dairy wastewater.
- Anaerobic treatment: Breaks down organic matter without oxygen. It can be suitable for wastewater with a high organic load and may generate biogas under appropriate operating conditions.
Some facilities combine anaerobic and aerobic processes. Anaerobic treatment can reduce a substantial portion of the organic load, while subsequent aerobic treatment helps further reduce residual biodegradable pollutants.
The selection depends on organic loading, wastewater characteristics, operating conditions, energy requirements, and the required effluent quality. Biological treatment also needs appropriate control of pH, loading rates, and potential inhibitory substances to maintain microbial activity.
5. Tertiary Treatment and Effluent Verification
After primary and biological treatment, additional processes may be needed to meet the facility’s discharge requirements or water reuse objectives.
Depending on the treatment results, these may include filtration, nutrient removal, disinfection, or membrane-based processes.
The final effluent should be monitored against the applicable discharge requirements. Relevant parameters may include pH, BOD, COD, total suspended solids (TSS), and other parameters specified by the applicable permit or regulation.
Routine monitoring also helps identify performance deterioration early, allowing operators to investigate potential causes before they lead to non-compliance.
Not every dairy facility requires the same tertiary treatment configuration. The need for additional processes should be determined by the intended discharge or reuse application.
Read Also: Water Treatment for Food and Beverage: A Practical Approach to Quality and Safety
Developing a Dairy Wastewater Treatment Approach Around Your Operations
Selecting the right dairy wastewater treatment process involves more than choosing individual technologies. The treatment stages must work together to accommodate production variations, manage pollutant loads, and maintain consistent effluent quality.
Lautan Air Indonesia (LAI) provides water and wastewater treatment capabilities that can support industrial facilities in developing treatment approaches suited to their operational requirements.
Depending on the project scope, this may involve engineering and treatment system development, process considerations, and operation and maintenance (O&M) support. A site-specific assessment can help identify the wastewater characteristics, treatment challenges, and operational requirements that should guide the treatment configuration.
For dairy manufacturers, this provides a practical starting point for evaluating existing treatment systems or planning improvements as production requirements change.
Looking to improve your dairy wastewater treatment performance? Contact Lautan Air Indonesia to discuss your wastewater characteristics, treatment objectives, and operational requirements.
Reference
- Slavov, A. K. (2016). Dairy Wastewaters – General Characteristics and Treatment Possibilities – A review. Food Technology and Biotechnology, 55(1), 14–28.
- Carvalho, F., Prazeres, A. R., & Rivas, J. (2013). Cheese whey wastewater: Characterization and treatment. The Science of the Total Environment, 445–446, 385–396.
- B, R. K., Bhuvaneshwari, S., Majeed, F., M, M. M., Jose, E., & Mohan, A. (2022). Different treatment methodologies and reactors employed for dairy effluent treatment – A review. Journal of Water Process Engineering, 46, 102622.
- Ye, M., & Li, Y. (2023). Methanogenic treatment of dairy wastewater: A review of current obstacles and new technological perspectives. The Science of the Total Environment, 866, 161447.
- Ahmad, T., Aadil, R. M., Ahmed, H., Rahman, U. U., Soares, B. C., Souza, S. L., Pimentel, T. C., Scudino, H., Guimarães, J. T., Esmerino, E. A., Freitas, M. Q., Almada, R. B., Vendramel, S. M., Silva, M. C., & Cruz, A. G. (2019). Treatment and utilization of dairy industrial waste: A review. Trends in Food Science & Technology, 88, 361–372.
